ADCs used in medical and industrial monitoring often transduce signals with short bursts of high activity followed by long idle periods. Examples include biopotential, sound, and accelerometer waveforms. Current approaches to save energy during periods of low signal activity include variable resolution and sample rate systems [1], asynchronous level-crossing ADCs [2], and ADCs that bypass bitcycles when the signal is within a predefined small window [3]. This work presents a signal-activity-based power-saving algorithm called LSB-first successive approximation (SA) that maintains a constant sample rate and resolution, scales logarithmically with signal activity, and does not inherently suffer from slope overload. LSB-first SA starts with an initial guess D of the current sample’s value and bitcycles the LSBs of D first, instead of the MSBs as in conventional SA. Because this ADC is targeted at signals with low average activity, an initial guess equal to
Frank M. Yaul, Anantha P. Chandrakasan
Massachusetts Institute of Technology, Cambridge, MA